Excess alpha chain is critical to the pathogenesis of the anemia of beta thalassemia. The object of this study is to characterize the rates and modes of elimination of excess alpha chain (precipitation, hydrolysis, etc.) from the thal erythroid cell. Certain groups of homozygotes for beta thal have a mild rather than a severe anemia (mild thalassemia, or thal intermedia) and in black patients with this mild syndrome rates of beta chain production are as markedly reduced as in typical severe (Cooley's) type patients. We propose, and are attempting to establish, that the kinetics of alpha chain removal are different in these patients and may account for the mildness of their anemia.